<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>pareq</title>
    <link rel="stylesheet" type="text/css" href="csound.css" />
    <meta name="generator" content="DocBook XSL Stylesheets V1.78.1" />
    <link rel="home" href="index.html" title="The Canonical Csound Reference Manual" />
    <link rel="up" href="OpcodesTop.html" title="Orchestra Opcodes and Operators" />
    <link rel="prev" href="pan.html" title="pan" />
    <link rel="next" href="partials.html" title="partials" />
  </head>
  <body>
    <div class="navheader">
      <table width="100%" summary="Navigation header">
        <tr>
          <th colspan="3" align="center">pareq</th>
        </tr>
        <tr>
          <td width="20%" align="left"><a accesskey="p" href="pan.html">Prev</a> </td>
          <th width="60%" align="center">Orchestra Opcodes and Operators</th>
          <td width="20%" align="right"> <a accesskey="n" href="partials.html">Next</a></td>
        </tr>
      </table>
      <hr />
    </div>
    <div class="refentry">
      <a id="pareq"></a>
      <div class="titlepage"></div>
      <a id="IndexPareq" class="indexterm"></a>
      <div class="refnamediv">
        <h2>
          <span class="refentrytitle">pareq</span>
        </h2>
        <p>pareq — 
      Implementation of Zoelzer's parametric equalizer filters.
          </p>
      </div>
      <div class="refsect1">
        <a id="idp132317728"></a>
        <h2>Description</h2>
        <p>
      Implementation of Zoelzer's parametric equalizer filters, with some modifications by the author.
    </p>
        <p>
      The formula for the low shelf filter is:
      </p>
        <div class="literallayout">
          <p><br />
omega = 2*pi*f/sr<br />
K     = tan(omega/2)<br />
	<br />
b0    = 1 + sqrt(2*V)*K + V*K^2<br />
b1    = 2*(V*K^2 - 1)<br />
b2    = 1 - sqrt(2*V)*K + V*K^2<br />
	<br />
a0    = 1 + K/Q + K^2<br />
a1    = 2*(K^2 - 1)<br />
a2    = 1 - K/Q + K^2<br />
      </p>
        </div>
        <p>
    </p>
        <p>
      The formula for the high shelf filter is:
      </p>
        <div class="literallayout">
          <p><br />
omega = 2*pi*f/sr<br />
K     = tan((pi-omega)/2)<br />
	<br />
b0    = 1 + sqrt(2*V)*K + V*K^2<br />
b1    = -2*(V*K^2 - 1)<br />
b1    = 1 - sqrt(2*V)*K + V*K^2<br />
	<br />
a0    = 1 + K/Q + K^2<br />
a1    = -2*(K^2 - 1)<br />
a2    = 1 - K/Q + K^2<br />
      </p>
        </div>
        <p>
    </p>
        <p>
      The formula for the peaking filter is:
      </p>
        <div class="literallayout">
          <p><br />
omega = 2*pi*f/sr<br />
K     = tan(omega/2)<br />
	<br />
b0 =  1 + V*K/2 + K^2<br />
b1 =  2*(K^2 - 1)<br />
b2 =  1 - V*K/2 + K^2<br />
	<br />
a0 =  1 + K/Q + K^2<br />
a1 =  2*(K^2 - 1)<br />
a2 =  1 - K/Q + K^2<br />
      </p>
        </div>
        <p>
    </p>
      </div>
      <div class="refsect1">
        <a id="idp132385760"></a>
        <h2>Syntax</h2>
        <pre class="synopsis">ares <span class="command"><strong>pareq</strong></span> asig, kc, kv, kq [, imode] [, iskip]</pre>
      </div>
      <div class="refsect1">
        <a id="idp132388016"></a>
        <h2>Initialization</h2>
        <p>
      <span class="emphasis"><em>imode</em></span> (optional, default: 0) -- operating mode
      </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem">
              <p>0 = Peaking</p>
            </li>
            <li class="listitem">
              <p>1 = Low Shelving</p>
            </li>
            <li class="listitem">
              <p>2 = High Shelving</p>
            </li>
          </ul>
        </div>
        <p>
    </p>
        <p>
      <span class="emphasis"><em>iskip</em></span> (optional, default=0) -- if non zero
    skip the initialisation of the filter. (New in Csound version
    4.23f13 and 5.0)
    </p>
      </div>
      <div class="refsect1">
        <a id="idp132393632"></a>
        <h2>Performance</h2>
        <p>
      <span class="emphasis"><em>kc</em></span> -- center frequency in peaking mode, corner frequency in shelving mode.
    </p>
        <p>
      <span class="emphasis"><em>kv</em></span> -- amount of boost or cut. A value less than 1 is a cut. A value greater than 1 is a boost. A value of 1 is a flat response.
    </p>
        <p>
      <span class="emphasis"><em>kq</em></span> -- Q of the filter (sqrt(.5) is no resonance)
    </p>
        <p>
      <span class="emphasis"><em>asig</em></span> -- the incoming signal
    </p>
      </div>
      <div class="refsect1">
        <a id="idp132398400"></a>
        <h2>Examples</h2>
        <p>
      Here is an example of the pareq opcode. It uses the file <a class="ulink" href="examples/pareq.csd" target="_top"><em class="citetitle">pareq.csd</em></a>.

      </p>
        <div class="example">
          <a id="idp132400176"></a>
          <p class="title">
            <strong>Example 599. Example of the pareq opcode.</strong>
          </p>
          <div class="example-contents">
            <p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
            <pre class="programlisting">
<span class="csdtag">&lt;CsoundSynthesizer&gt;</span>
<span class="csdtag">&lt;CsOptions&gt;</span>
<span class="comment">; Select audio/midi flags here according to platform</span>
<span class="comment">; Audio out   Audio in    No messages</span>
-odac           -iadc     -d     <span class="comment">;;;RT audio I/O</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o pareq.wav -W ;;; for file output any platform</span>
<span class="csdtag">&lt;/CsOptions&gt;</span>
<span class="csdtag">&lt;CsInstruments&gt;</span>

<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">kr</span>  <span class="op">=</span> 4410
<span class="ohdr">ksmps</span> <span class="op">=</span> 10
<span class="ohdr">nchnls</span> <span class="op">=</span> 2

<span class="oblock">instr</span> 15
  ifc     <span class="op">=</span>       p4                       <span class="comment">; Center / Shelf</span>
  kq      <span class="op">=</span>       p5                       <span class="comment">; Quality factor sqrt(.5) is no resonance</span>
  kv      <span class="op">=</span>       <span class="opc">ampdb</span>(p6)                <span class="comment">; Volume Boost/Cut</span>
  imode   <span class="op">=</span>       p7                       <span class="comment">; Mode 0=Peaking EQ, 1=Low Shelf, 2=High Shelf</span>
  kfc     <span class="opc">linseg</span>  ifc<span class="op">*</span>2, p3, ifc<span class="op">/</span>2
  asig    <span class="opc">rand</span>    5000                     <span class="comment">; Random number source for testing</span>
  aout    <span class="opc">pareq</span>   asig, kfc, kv, kq, imode <span class="comment">; Parmetric equalization</span>
          <span class="opc">outs</span>    aout, aout               <span class="comment">; Output the results</span>
<span class="oblock">endin</span>


<span class="csdtag">&lt;/CsInstruments&gt;</span>
<span class="csdtag">&lt;CsScore&gt;</span>

<span class="comment">; SCORE:</span>
  <span class="comment">;   Sta  Dur  Fcenter  Q        Boost/Cut(dB)  Mode</span>
  <span class="stamnt">i</span>15 0    1    10000   .2          12             1
  <span class="stamnt">i</span>15 +    .    5000    .2          12             1
  <span class="stamnt">i</span>15 .    .    1000    .707       -12             2
  <span class="stamnt">i</span>15 .    .    5000    .1         -12             0
  <span class="stamnt">e</span>


<span class="csdtag">&lt;/CsScore&gt;</span>
<span class="csdtag">&lt;/CsoundSynthesizer&gt;</span>
</pre>
          </div>
        </div>
        <p><br class="example-break" />
    </p>
      </div>
      <div class="refsect1">
        <a id="idp132404496"></a>
        <h2>Credits</h2>
        <p>
      </p>
        <table border="0" summary="Simple list" class="simplelist">
          <tr>
            <td>Hans Mikelson</td>
          </tr>
          <tr>
            <td>December 1998</td>
          </tr>
        </table>
        <p>
    </p>
        <p>New in Csound version 3.50</p>
      </div>
    </div>
    <div class="navfooter">
      <hr />
      <table width="100%" summary="Navigation footer">
        <tr>
          <td width="40%" align="left"><a accesskey="p" href="pan.html">Prev</a> </td>
          <td width="20%" align="center">
            <a accesskey="u" href="OpcodesTop.html">Up</a>
          </td>
          <td width="40%" align="right"> <a accesskey="n" href="partials.html">Next</a></td>
        </tr>
        <tr>
          <td width="40%" align="left" valign="top">pan </td>
          <td width="20%" align="center">
            <a accesskey="h" href="index.html">Home</a>
          </td>
          <td width="40%" align="right" valign="top"> partials</td>
        </tr>
      </table>
    </div>
  </body>
</html>
